Concrete Slab Cost in Washington
Quick answer: a 4-inch concrete slab in Washington costs about $7.00 – $13.50 per sq ft installed, 8% above the U.S. average. A 12 × 12 ft patio runs about $1,190 – $2,070, a 24 × 24 ft garage floor $4,520 – $7,970 and a 20 × 40 ft driveway $6,210 – $10,980.
Washington concrete costs above the national average in our model, and the Seattle metro higher again. The state splits at the Cascades: rain and mild winters in the west, real freeze-thaw winters and dry summers in the east.
Concrete Prices in Washington by Project
| Project | Washington installed | Per sq ft | U.S. average | DIY materials |
|---|---|---|---|---|
| 12 × 12 ft patio | $1,190 – $2,070 | $8.00 – $14.50 | $1,130 – $1,970 | $540 – $770 |
| 10 × 12 ft shed slab | $1,020 – $1,760 | $8.50 – $15.00 | $970 – $1,680 | $480 – $670 |
| 20 × 20 ft slab | $2,990 – $5,350 | $7.00 – $13.50 | $2,810 – $5,060 | $1,180 – $1,820 |
| 24 × 24 ft garage floor (5 in) | $4,520 – $7,970 | $7.50 – $14.00 | $4,250 – $7,540 | $1,920 – $2,840 |
| 20 × 40 ft driveway (5 in) | $6,210 – $10,980 | $7.50 – $14.00 | $5,820 – $10,380 | $2,580 – $3,860 |
| 30 × 40 ft shop floor (6 in) | $9,820 – $17,110 | $8.00 – $14.50 | $9,190 – $16,140 | $4,390 – $6,310 |
4-inch slabs unless shown. Installed: forms, broom finish and labor, up to vapor barrier, #4 rebar and contractor overhead and profit. DIY: concrete (ready-mix or 80-lb bags, whichever is cheaper) and forms, up to vapor barrier and rebar. Excavation, gravel base and permits are extra.
Metro Areas
Prices in the biggest metro areas differ from the state as a whole, mainly because of labor costs.
| Area | Factor | Slab per sq ft | 12 × 12 patio | 24 × 24 garage | 20 × 40 driveway |
|---|---|---|---|---|---|
| Washington (statewide) | 1.08 | $7.00 – $13.50 | $1,190 – $2,070 | $4,520 – $7,970 | $6,210 – $10,980 |
| Seattle metro, WA | 1.12 | $7.50 – $14.00 | $1,230 – $2,120 | $4,660 – $8,190 | $6,400 – $11,280 |
Building a Slab in Washington
| Weathering (IRC) | Moderate west of the Cascades; severe east of them. |
|---|---|
| Concrete strength | 3,000 PSI is common west of the Cascades; 3,500 PSI air-entrained in eastern Washington and the mountains. 3,500 PSI ready-mix runs about $150 – $184 per yd³ here. |
| Frost depth | About 12 in around Seattle and on the west side; around 24 in or more in eastern Washington. |
| Soil | Glacial till and clay around Puget Sound, which drain slowly; sandy and silty soils in the east. |
| Pouring season | West side: plan around the rain from about October to April and keep plastic ready to cover a fresh slab. East side: spring to fall. |
- Rain on a fresh slab washes out the surface and weakens it; west-side crews watch the forecast and tent or cover the pour.
- Slow-draining till under Puget Sound slabs needs a gravel base and a slope away from the house.
- East of the Cascades, use air-entrained concrete and keep salt off new slabs.
Frost depths and permit rules are set by your city or county; check with the local building department before you dig. A permit for a small residential slab or driveway typically costs about $50 – $350.
Price Your Own Slab in Washington
The calculator below starts at Washington prices. Enter your size, thickness, finish and reinforcement; if you have local prices for ready-mix or labor, type them over the defaults.
Concrete Slab Cost & Volume Estimator
Precision multi-layer project budgeting: Materials, Sub-Base, Reinforcement, Labor & Equipment
Picking a location sets the ready-mix, excavation and labor rates below to that area's typical level. You can still type your own local prices afterwards. Slab prices by state.
Closer spacing uses more steel and raises the rebar cost.
Not charged when bagged concrete is selected.
A scaled plan of your slab: rebar grid at the spacing you chose, support chairs about every 3 to 4 ft, and the recommended control-joint saw cuts (2.5 times the thickness in inches, in feet, capped at 15 ft). It redraws as you change the inputs.
| Scope Item / Material Description | Amount |
|---|
Enter the total your contractor quoted. We compare it with a benchmark for the same slab and scope you set in the calculator: materials at your entered prices plus labor at the regional standard rate, before any overhead or profit. Make sure the calculator scope (base, rebar, finish, pump, demolition) matches what the bid includes.
Optional: enter the bid's line items to see where the markup sits
Enter the forecast for pour day. The check follows ACI 306R (cold weather) and ACI 305R (hot weather) and estimates the surface evaporation rate that drives plastic shrinkage cracking.
How These Prices Are Worked Out
These are modelled prices, not quotes collected from Washington contractors. Each project is priced with the same line items as the slab cost calculator at national unit prices, then Washington's location factor of 1.08 is applied to ready-mix concrete and labor, as the calculator does when you pick Washington. Bagged concrete, forms, rebar and the delivery fee stay at national prices. The factors are approximate, set by our editors to reflect typical construction cost differences between states; the full method is in the 2026 concrete price report.
Have a quote already? Check it with the concrete quote checker, which uses the same factors.
Washington Concrete Questions
About $7.00 to $13.50 per sq ft installed for a 4-inch slab with forms, a broom finish and labor, 8% above the national average. A 12 x 12 ft patio runs about $1,190 to $2,070 and a 24 x 24 ft garage floor (5 in) about $4,520 to $7,970. Excavation, gravel and permits are extra.
A 20 x 40 ft driveway, 5 inches thick with rebar and a broom finish, costs about $6,210 to $10,980 installed in Washington ($7.50 to $14.00 per sq ft). Removing an old driveway and the street apron are extra.
About $146 to $173 per cubic yard for 3,000 PSI ready-mix before delivery fees, and about $150 to $184 for 3,500 PSI. Small loads add a short-load fee of $80 to $200 or more.
In the Seattle area our model puts 3,000 PSI ready-mix at about $151 to $179 per cubic yard before delivery, and a 4-inch slab at about $7.50 to $14.00 per sq ft installed, 12% above the U.S. average. A 12 x 12 ft patio runs about $1,230 to $2,120 and a 20 x 40 ft driveway about $6,400 to $11,280.
Light rain before the pour is fine if the base is not muddy or flooded. Rain during finishing is the problem: it adds water to the surface and weakens it. Crews cover the slab with plastic or a tent, and reschedule if heavy rain is forecast.
They are the site's national cost model with Washington's location factor (1.08) applied to ready-mix and labor, the same thing the calculator does when you pick Washington. They are modelled estimates, not prices collected from Washington contractors; get local quotes before you build.